Disclosed herein are hot melt or phase change inks and methods for the use thereof. More specifically, disclosed herein are hot melt or phase change inks particularly suitable for use in phase change ink jet printing processes with reduced energy requirements. One embodiment is directed to a phase change ink comprising (a) a carbon black pigment, (b) a bis-urethane, and (c) a phase change ink carrier, said carrier comprising (i) a branched triamide and (ii) a Fischer-Tropsch wax having an average peak molecular weight of from about 300 to about 800 and a polydispersity of from about 1.001 to about 3. Also disclosed herein is a process which comprises (1) incorporating into an ink jet printing apparatus a phase change ink comprising (a) a carbon black pigment, (b) a bis-urethane, and (c) a phase change ink carrier, said carrier comprising (i) a branched triamide and (ii) a Fischer-Tropsch wax having an average peak molecular weight of from about 300 to about 800 and a polydispersity of from about 1.001 to about 3; (2) melting the ink; and (3) causing droplets of the melted ink to be ejected in an imagewise pattern onto a substrate.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. No. 3,653,932, U.S. Pat. No. 4,390,369, U.S. Pat. No. 4,484,948, U.S. Pat. No. 4,684,956, U.S. Pat. No. 4,851,045, U.S. Pat. No. 4,889,560, U.S. Pat. No. 5,006,170, U.S. Pat. No. 5,151,120, U.S. Pat. No. 5,372,852, U.S. Pat. No. 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
Many phase change inks demonstrate a propensity to weep in the printhead of an inkjet printing apparatus. Weeping refers to the uncontrolled flow of ink from the nozzles of an ink jet printhead onto the face of the printhead, as can occur following the passage of the wiper blade across the nozzles or ink jet heads during a purge cycle. Some of the ramifications of weeping include excessive ink purge volume, color mixing in the jets resulting in poor color reproduction in subsequent prints, and potential jetting reliability/robustness issues.
In pigment-based inks in particular, such as those having carbon black particles, weeping can be observed. Some challenges exist in effectively dispersing pigments in current phase change ink vehicles. For example, the non-polar components in the ink vehicle can hinder pigment stability in the ink. Dispersants can be used to stabilize the pigment particles in the non-polar ink vehicle, but while some dispersants assist with stability, they do not address weeping.
U.S. Pat. No. 6,860,930 (Wu et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition comprising (a) a colorant and (b) a carrier comprising a polyamide, wherein the polyamide component of the carrier contains at least about 10 percent by weight of a branched triamide.
U.S. Patent Publication 2005/0130054 (Yuan et al.), the disclosure of which is totally incorporated herein by reference, discloses wax based inks for phase change/hot melt inkjet printing or thermal transfer printing applications. Also disclosed are waxes useful for toners for use in electrostatographic printing applications. Both materials are prepared using a wax having a narrow melting range. The narrow melting range of the wax reduces energy requirements in printing applications. The use of the waxes also promotes release for high speed printing and especially promotes fast drying in wax based ink applications.
U.S. Pat. No. 6,001,904 (Matzinger et al.), the disclosure of which is totally incorporated herein by reference, discloses phase change (hot melt) ink compositions for use in a phase change (hot melt) ink jet recording device in which recording is conducted by thermally melting the ink at a temperature above ambient temperature (20° C.) to provide prints that possess high quality images, scratch resistance, abrasion resistance, low-temperature storage stability and flexibility, offset and pick resistance, adhesion, and other desired properties to comprise: (a) from about 0.1% to about 30% of one or more colorants; and (b) from about 0.1 to about 99.9% of one or more reversibly-crosslinked-polymers. Components other than those listed above can be included in the ink compositions to achieve specific printer, substrate, or end use requirements. Furthermore, the invention also includes methods for the preparation of reversibly-crosslinked-polymers and for their use in the above-described inks.
U.S. Pat. No. 7,311,768 (Wu et al.), the disclosure of which is totally incorporated herein by reference, discloses a phase change ink comprising (a) a colorant and (b) a phase change ink carrier, said carrier comprising (i) an amide and (ii) a Fischer-Tropsch wax having an average peak molecular weight of from about 300 to about 800 and a polydispersity of from about 1.001 to about 3. Also disclosed is a process which comprises (1) incorporating into an ink jet printing apparatus a phase change ink comprising (a) a colorant and (b) a phase change ink carrier, said carrier comprising (i) an amide and (ii) a Fischer-Tropsch wax having an average peak molecular weight of from about 300 to about 800 and a polydispersity of from about 1.001 to about 3; (2) melting the ink; and (3) causing droplets of the melted ink to be ejected in an imagewise pattern onto a substrate.
U.S. Pat. No. 6,858,070 (Wong et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising (a) an ink carrier which comprises a monoamide, a tetra-amide, or a mixture thereof; (b) a polyalkylene succinimide; and (c) pigment particles. Also disclosed is an ink composition comprising (a) an ink carrier, (b) a polyalkylene succinimide, and (c) pigment particles, said ink having a conductivity greater than 1×10−8 Siemens per centimeter. Also disclosed is an ink set comprising (1) a first ink comprising (a) an ink carrier, (b) a polyalkylene succinimide, and (c) pigment particles, and (2) a second ink comprising a dye colorant and a second ink carrier, wherein the first ink carrier contains substantially the same components as the second ink carrier.
U.S. Pat. No. 6,878,198 (Drappel et al.), the disclosure of which is totally incorporated herein by reference, discloses phase change ink compositions comprising (a) an ink carrier comprising a monoamide and a tetra-amide, and (b) pigment particles having oxygen-containing functional groups on the surfaces thereof. Also disclosed are processes for preparing a phase change ink which comprise (a) melting a tetra-amide which is solid at about 25° C.; (b) admixing with the molten tetra-amide pigment particles having oxygen-containing functional groups on the surfaces thereof; (c) maintaining the mixture of pigment and tetra-amide at a temperature of at least about 100° C. and at a temperature of no more than about 200° C. for a period sufficient to enable the molten tetra-amide to wet the pigment particle surfaces; (d) subsequent to wetting of the pigment particle surfaces with the molten tetra-amide, adding to the mixture a monoamide; (e) subsequent to addition of the monoamide, subjecting the resulting mixture to high shear mixing; and (f) subsequent to subjecting the mixture to high shear mixing, optionally adding to the mixture additional ink ingredients.
U.S. Pat. No. 7,186,762 (Wong et al.), the disclosure of which is totally incorporated herein by reference, discloses a process for preparing a phase change ink composition which comprises (a) a phase change ink carrier, said carrier comprising at least one nonpolar component and at least one polar component, and (b) pigment particles, said process comprising (1) selecting at least one of the polar carrier components to be a pigment particle dispersant; (2) admixing the pigment particles with the dispersant; (3) extruding the mixture of pigment particles and dispersant in an extruder at a temperature that is at or above about the peak crystallization temperature of the dispersant and below about the peak melting temperature of the dispersant, thereby forming a pigment dispersion; (4) subsequent to extrusion of the pigment dispersion, adding to the pigment dispersion any remaining polar components and the nonpolar component; and (5) subjecting the resulting mixture of pigment dispersion, polar component, and nonpolar component to high shear mixing to form an ink.
U.S. Pat. No. 5,053,079 (Haxell et al.), the disclosure of which is totally incorporated herein by reference, discloses a dispersed, pigmented hot melt ink containing a thermoplastic vehicle, a colored pigment, and a dispersing agent to inhibit settling or agglomeration of pigment when the ink is molten comprising an isocyanate-modified microcrystalline wax or lignite wax in an amount of 2 to 100 weight percent of the weight of the vehicle. Preferred is the isocyanate-modified microcrystalline wax marketed as Petrolite WB17.
While known compositions and processes are suitable for their intended purposes, a need remains for improved phase change ink compositions. In addition, a need remains for phase change inks that can be jetted at temperatures below about 125° C. Further, a need remains for phase change inks that can be jetted with reduced energy requirements. Additionally, a need remains for phase change inks that can be jetted with less expensive printheads. There is also a need for phase change inks that enable improved thermal stability of the inks manifested as the color's stability over time when heated in printers. In addition, there is a need for phase change inks that enable improved printer reliability. Further, there is a need for phase change inks that enable quick recovery times from standby mode. Additionally, there is a need for phase change inks that enable printing with “instant-on” mode. A need also remains for phase change inks that exhibit desirable viscosity values at reduced printing temperatures. In addition, a need remains for phase change inks that enable the aforementioned advantages and also exhibit good printing characteristics, such as transfixing properties (including dither and solid fill dropout performance), acceptable missed jets, folding and creasing performance, gloss, color intensity, recovery after standby mode, and the like. Further, a need remains for phase change inks that generate images with improved hardness. Additionally, a need remains for phase change inks that generate images with improved gloss. There is also a need for phase change inks that exhibit reduced sweating; sweating is a problem wherein some ink ingredients migrate to the surface of solid ink sticks and aggregate at the ink stick surface inside the printer; the sticky “sweat” gradually drains down to the bottom and can cause the ink sticks to be difficult to slide in the ink load racks in the printers. In addition, there is a need for phase change inks that generate images with reduced showthrough when printed on paper substrates. Further, there is a need for phase change inks that exhibit reduced clogging of printheads while exhibiting all of the aforementioned advantages. Additionally, there is a need for phase change inks that enable reduced standby temperatures of phase change ink jet printheads without leading to clogging of the printhead. A need also remains for phase change inks with desirably low freezing points. In addition, a need remains for phase change inks that transfer efficiently from an intermediate transfer member to a final recording substrate with reduced pixels left on the intermediate transfer member when the intermediate transfer member is at a desirably high temperature to enable efficient transfer member cooling and avoid automatic printer shutoff from heating of the intermediate transfer member by the ink, while also enabling jetting of the ink at a desirably low temperature. Further, a need remains for phase change inks that exhibit desirably high smudge temperatures when still-hot prints pass along guidance tracks in the printer, thereby reducing accumulation of ink along these guidance tracks that could later be transferred to blank paper. Additionally, a need remains for phase change inks that exhibit the above advantages and can also be prepared at desirably low costs. There is also a need for phase change inks that have desirably high cohesive failure temperatures. There is also a need for phase change inks that have desirably high cohesive failure temperatures. In addition, there is a need for phase change inks that exhibit reduced showthrough of printed images on the backside of paper substrates, particularly when aged at relatively high temperatures. Further, there is a need for phase change inks that exhibit reduced weeping from the printhead.